Testosterone (T) is a medication and naturally occurring steroid hormone. It is used to treat male hypogonadism, gender dysphoria, and certain types of breast cancer. It may also be used to increase athletic ability in the form of doping. It is unclear if the use of testosterone for low levels due to aging is beneficial or harmful. Testosterone can be used as a gel or patch that is applied to the skin, injection into a muscle, tablet that is placed in the cheek, or tablet that is taken by mouth.
Common side effects of testosterone include acne, swelling, and breast enlargement in men. Serious side effects may include liver toxicity, heart disease, and behavioral changes. Women and children who are exposed may develop masculinization. It is recommended that individuals with prostate cancer not use the medication. It can cause harm to the baby if used during pregnancy or breastfeeding. Testosterone is in the androgen family of medications.
Testosterone was first isolated in 1935, and approved for medical use in 1939. Rates of use have increased three times in the United States between 2001 and 2011. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2020, it was the 172nd most commonly prescribed medication in the United States, with more than 3million prescriptions.
Medical uses
The primary use of testosterone is the treatment of males with too little or no natural testosterone production, also termed hypogonadism or hypoandrogenism (androgen deficiency). This treatment is referred to as hormone replacement therapy (HRT), or alternatively, and more specifically, as testosterone replacement therapy (TRT) or androgen replacement therapy (ART). It is used to maintain serum testosterone levels in the normal male range. Decline of testosterone production with age has led to interest in testosterone supplementation.
A 2020 guideline from the American College of Physicians supports the discussion of testosterone in adult men with age-related low levels of testosterone who have sexual dysfunction. They recommend yearly evaluation regarding possible improvement and, if none, to discontinue testosterone; physicians should consider intramuscular treatments, rather than transdermal treatments, due to costs and since the effectiveness and harm of either method is similar. Testosterone treatment for reasons other than possible improvement of sexual dysfunction may not be recommended.
Deficiency
Testosterone deficiency (also termed hypotestosteronism or hypotestosteronemia) is an abnormally low testosterone production. It may occur because of testicular dysfunction (primary hypogonadism) or hypothalamic–pituitary dysfunction (secondary hypogonadism) and may be congenital or acquired.
Low levels due to aging
Testosterone levels may decline gradually with age. The United States Food and Drug Administration (FDA) stated in 2015 that neither the benefits nor the safety of testosterone supplement have been established for low testosterone levels due to aging. The FDA has required that labels on testosterone include warnings about increased risk of heart attacks and stroke.
Transgender men
To take advantage of its virilizing effects, testosterone is administered to transgender men and other transmasculine individuals as part of masculinizing hormone therapy, titrated to clinical effect with a "target level" of the average male's testosterone level.
Women
Testosterone therapy is effective in the short-term for the treatment of hypoactive sexual desire disorder (HSDD) in women. However, its long-term safety is unclear. Because of a lack data to support its efficacy and safety, the Endocrine Society recommends against the routine use of testosterone in women to treat low androgen levels due to hypopituitarism, adrenal insufficiency, surgical removal of the ovaries, high-dose corticosteroid therapy, or other causes. Similarly, because of a lack of data to support its efficacy and safety, the Endocrine Society recommends against the use of testosterone in women to improve general well-being, to treat infertility, sexual dysfunction due to causes other than HSDD, or to improve cognitive, cardiovascular, metabolic, and/or bone health.